1. Field of the Invention
The invention relates to a glazed element having a high insulating ability and intended to be fastened to a bearing structure. It relates more particularly to the fastening of glazed elements having a high insulating ability to a bearing structure using a technique including fastening the elements by mechanical bolting points usually located at each of their corners.
2. Description of the Related Art
Glazed elements fastened to a bearing structure are known as structural glazings (SG) or bolted exterior glazings. They make it possible to obtain, for example, exterior walls or facades for buildings consisting entirely of glazed elements, some being transparent and others being opaque. Such facades have a minimum of surface discontinuities as seen from outside.
However, achieving an aesthetically pleasing effect must not be made at the expense of the reliability of the fastening system, and the design of the point connections must take into account various requirements from a mechanical standpoint. Thus, the connections must guarantee fastening between the glazed element and the bearing structure which is solid and effective and, in particular, must support the weight of the glazed element without risk of breakage. In addition, the glazed element, once it has been fitted, must be capable of "responding" without breaking to various kinds of stresses, particularly to stresses which will have a tendency to bend it, e.g., those created by wind-type atmospheric conditions. The connections therefore have to allow for a few degrees of bending of the glazed element.
It is usual, to obtain thermal and/or acoustic insulation, to produce insulating glazing panels comprising two substrates separated from each other by a relatively wide air cavity, the sealing of which is provided by a peripheral seal in a known manner. Each of the substrates may be a single glass plate or may have a laminated structure. However, in the case of such multiple glazings, only one of the substrates is conventionally joined to the bearing structure by a fastening system. This raises the risk that the other substrates which are associated with the fastened substrate will overstress the peripheral seals, which are only designed to provide sealing of the assembly, and not to withstand high shear stresses or the weight of these other substrates.
It is therefore important, in the case of multiple glazings, to provide connections between the substrates which make it possible to reduce these stresses at the seals, the purpose of the connections being to transfer at least part of the weight of each substrate not fastened to the structure to the substrate which is fastened thereto.
Various SG glazing fittings have already been proposed. Thus, EP-A-0,506,522 and EP-A-0-655,543 describe systems for mechanically connecting SG glazing panels to their bearing structure, which make it possible to "bolt" the glazed element reliably to its structure while still allowing it to be able to bend in a durable and controlled manner. In the case of multiple glazing, these systems also make it possible to realign the successive holes drilled in each of the panes of the glazing, this being achieved by means of a system of eccentric rings in one of the holes. The flexibility of the glazing is improved using these types of connection, but the manufacture of these fastening systems is quite demanding as there must be perfect matching between the various elements. Great accuracy with regard to dimensioning is therefore necessary, which leads to high manufacturing costs and significant manufacturing complexity.
Moreover, the usual insulating glazing panels provide thermal insulation which is regarded as being unsatisfactory for some applications. In order to remedy this, it is known to produce glazing panels consisting of three glass sheets, in which one of the air cavities is replaced by a gas such as krypton. These glazing panels have markedly proved thermal insulation properties but have a thickness and weight which make them difficult to use in SG type arrangements.